From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Thu, 25 Jan 2001 18:53:40 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Thu, 25 Jan 2001 18:53:29 -0500 Received: from diver.doc.ic.ac.uk ([146.169.1.47]:47634 "EHLO diver.doc.ic.ac.uk") by vger.kernel.org with ESMTP id ; Thu, 25 Jan 2001 18:53:21 -0500 To: "Stephen C. Tweedie" Cc: "Eric W. Biederman" , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: limit on number of kmapped pages In-Reply-To: <20010125181621.W11607@redhat.com> From: David Wragg Date: 25 Jan 2001 23:53:16 +0000 In-Reply-To: "Stephen C. Tweedie"'s message of "Thu, 25 Jan 2001 18:16:21 +0000" Message-ID: User-Agent: Gnus/5.0807 (Gnus v5.8.7) XEmacs/21.1 (Bryce Canyon) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org "Stephen C. Tweedie" writes: > On Wed, Jan 24, 2001 at 12:35:12AM +0000, David Wragg wrote: > > > > > And why do the pages need to be kmapped? > > > > They only need to be kmapped while data is being copied into them. > > But you only need to kmap one page at a time during the copy. There > is absolutely no need to copy the whole chunk at once. The chunks I'm copying are always smaller than a page. Usually they are a few hundred bytes. Though because I'm copying into the pages in a bottom half, I'll have to use kmap_atomic. After a page is filled, it is put into the page cache. So they have to be allocated with page_cache_alloc(), hence __GFP_HIGHMEM and the reason I'm bothering with kmap at all. David Wragg - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/